This invention relates to fusion bonded pile carpet and carpet tile which use a non-hot melt latex as the yarn-locking adhesive and to production methods for such carpet and carpet tile.
Pile carpet is generally manufactured in one of two ways. The pile yarn may be woven or tufted through a primary backing. The yarn is then secured to the primary backing with an adhesive precoat. This type of carpet in which yarn is mechanically as well as adhesively attached to backing is generally termed "woven" or "tufted" carpet. Alternatively, yarn may be cut or looped and positioned to form a pile layer that is then secured to the primary backing with adhesive. Carpet of this type is commonly referred to as "fusion bonded" carpet.
Fusion bonded carpet is generally categorized by the way the pile yarn layer is produced. In an "I-tuft" process, yarn is first cut into short, straight strands, and then the yarn ends are bonded to a primary support backing with adhesive. In a "U-tuft" process, a pile yarn layer is formed of folded yarn strands. The folded sections of the strands are then secured to the primary backing with an adhesive layer such that in the final carpet product, both ends of each cut strand protrude from the adhesive base.
The most widely used method of manufacture of fusion bonded carpet presently involves the use of a nonlatex PVC (polyvinyl chloride) plastisol formulation as the bonding adhesive. Typically, PVC plastisol is dispensed over a support layer to form an adhesive layer that penetrates into the support layer. The adhesive layer is then contacted with pile forming yarn. The PVC plastisol is cured, creating a product in which the yarn fibers are secured in the PVC layer and thereby bonded to the support layer. Increased strength may be obtained by bonding a secondary backing to the support layer.
In order to make a durable fusion bonded carpet in which the support layer does not peel away from the secondary backing, the adhesive which has permeated into the support layer must contact and bond with the material forming or adhering the secondary backing. The use of a nonlatex plasticized PVC as the yarn locking adhesive limits the variety of backing structures that may be applied to the carpet. This is true because nonlatex PVC plastisol does not bond strongly to common carpet backing materials such as bitumen, EVA (ethylene-vinylacetate), APP (atactic polypropylene), hot melts, urethanes, and SBR (styrene-butadiene). Furthermore, PVC plastisol is relatively expensive.
A fusion bonded carpet which does not use PVC as the pile yarn adhesive is described in U.S. Pat. Nos. 4,371,576 and 4,576,665. The carpet is prepared by forcing a heated hot melt adhesive through a liquid permeable support layer to contact with the pile forming yarn on the opposite side of the base layer. The adhesive is then allowed to cool, during which time the pile forming yarn and support layer are secured.
Hot melt adhesives have been known for many years and usually include a thermoplastic resin, wax and a polymeric adhesive. Typically such compositions have a melt viscosity of significantly less than about 200,000 cps, and more typically, less than 100,000 cps at 300.degree. F., to enable them to have sufficient flow characteristics at the application temperature. Hot melt adhesives are applied at high temperature, and cured by cooling.